This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7119 from an application for ALC And Size Regulation Circuit Of Display Apparatus earlier filed in the Korean Industrial Property Office on the 13th of Feb. 1999, and there duly assigned Ser. No. 5286/1999, a copy of which application is annexed hereto.
The present invention relates to a display apparatus. More specifically, the present invention relates to a circuit for regulating the brightness and size of picture in a display apparatus, in which a picture brightness regulating circuit and a picture size regulating circuit are organically coupled together, and the picture brightness and size are decided by utilizing composite adjusting signals of a microcomputer, in view of the fact that the picture brightness and size are decided by the beam currents flowing from a fly back transformer to a cathode ray tube.
Generally, the brightness regulating circuit of a display apparatus prevents the brightness level of picture from rising too high, so that the picture brightness of the display apparatus would be constant all the time. Therefore, the intensities of the beam currents which are supplied to the cathode ray tube are fed back to the brightness regulating circuit. Thus if the intensity of the feedback beam current is higher than a certain level, then the clamp levels of the RGB video signals which are inputted into the brightness regulating circuit are made to be restricted by a predetermined level, so that the intensities of the beam currents would not rise any more.
Meanwhile, the picture size regulating circuit of the display apparatus regulates the picture size which is varied in accordance with the variation of the high voltage. This picture size regulating circuit is generally applied to a high voltage/horizontal deflection integral type display apparatus in which the high voltage is not constant, and in which the picture size is varied in accordance with the intensity of the beam current.
In other words, if the high voltage is varied, then the picture size is varied, and if the high voltage is varied, then the intensities of the beam currents are also varied. As described above, there is a close relationship between the variation of the high voltage and the variation of the intensities of the beam currents. Therefore, the picture size regulating circuit detects any variation of the intensities of the beam currents, and decides the picture size based on the detected intensities of the beam currents. Therefore, this picture size regulating circuit can easily regulate the picture size in the high voltage/horizontal deflection integral type display apparatus.
What is needed is the maximum brightness restriction line and the picture size regulating degree are decided by the composite adjusting signals of the microcomputer. Therefore, the manufacturing time can be saved during the manufacture of the display apparatus, and therefore, the productivity can be improved. Further, the constitution of the brightness and picture size regulating circuit section is very simple, and therefore, the economy is improved during its designing.
Therefore it is an object of the present invention to provide a circuit for regulating the brightness and picture size in a display apparatus, in which a picture brightness regulating circuit and a picture size regulating circuit are organically coupled together, and the picture brightness and size are decided by utilizing composite adjusting signals of a microcomputer.
In achieving the above object, in a display apparatus for receiving and amplifying RGB signals from a computer main body to output them to a cathode ray tube, for supplying a high voltage from a fly back transformer to the cathode ray tube, and for carrying out horizontal deflections by a horizontal deflecting circuit, the circuit for regulating the brightness and picture size for the display apparatus according to the present invention includes: a current sensing section for sensing intensities of beam currents incoming into the cathode ray tube; a microcomputer for deciding a lower limit of a terminal voltage if the terminal voltage is lowered, the terminal voltage being anti-proportional to the beam current as sensed by the current sensing section; and a brightness and picture size regulating circuit section for deciding an upper limit of the terminal voltage in relation to an internal power and an internal impedance of a video pre-amplifier, for outputting brightness regulating signals to the video pre-amplifier to adjust the clamp level of RGB video signals if the terminal voltage departs from the lower limit of the microcomputer, and for outputting horizontal/vertical size regulating signals to a deflecting circuit section to regulate a picture size.
In the conventional display apparatus, a brightness regulating circuit and a picture size regulating circuit are separately made. And brightness regulating signals and horizontal/vertical size regulating signals inputted to the brightness regulating circuit and a picture size regulating circuit are outputted separately from the microcomputer. However, in the present invention, brightness and picture size regulating circuit section is made as one circuit and composite adjusting signals outputted from a microcomputer are inputted into the brightness and picture size regulating circuit section in order to adjust brightness and picture size of a monitor.